Transformer



1931- G. A. THORNTON ET AL 1,818,539

TRANSFORMER Original Filed March 12 1927 HW M IIHI .99

INVENTOR GL4. T/mrmon W Remingfo .1 I all Patented Aug. 11, 1931 UNITED STATES PATENT OFFICE GEGEGE A. THORNTON, 0F SCHENECTAIDY, NEW YORK, AND WOLCOTT REMINGTON, 9F SWAMPSCOTT, MASSACHUSETTS, ASSIGNORS, BY MESNE ASSIGNMENTS, T0 THOMfiON-GIBB ELECTRIC WELDING- COMFANY, A CORPORATION OF MASSACHU- TRANSFORMER briginel application filed March 12, 192?, Serial No. 174,778. Divided and this application filed January 28,

This invention relates to current limiting and regulating devices for alternating current electrical apparatus.

It is one of the primary objects of the invention to provide an improved regulating exciting coil.

This invention relates particularly to a current and voltage regulating mechanism of general application adaptable to wide variations in the output of the secondary of the transformer without undue transformer loss. I

These and other objects will appear more fully from. the following description when considered in connection with the drawings in which:

Fig. 1 illustrates a transformer constructed according to our invention.

Fig. 2 illustrates a modification thereof.

lnthe drawings (Fig. 1) the magnetizable core 102 includes a main magnetic core portion formed with limbs 98 and 100 connected by the upper and lower yoke portions l5 andconstituting a closed path for the magnetic lines of force. The primary coil 10% is mounted" in embracing relation to the limb 98 and the secondary coil 112 similarly embraces the limb 100. The construction referred to above constitutes a usual type of transformer to which we have shown our invention as applied.

in order vary the operation of the transformer we have provided an auxiliary magnetizable core portion 09 constructed integrally or in intimate relation to the main core. The limb and yokes of the auxiliary core portion together with the main core form two complete flux-paths with one portion 100 in common.

An auxiliary primary winding 106 cm braces the auxiliary limb 99 in flux-produc- Serial No. 250,096.

ing relation to the same. in order to vary the effective turns of the auxiliary winding 106 we have illustrated the same as provided with a usual five-point regulator 108 and a short circuit connection 107. This construction permits the variation of the number of turnsin the auxiliary winding from. zero to the maximum number for which the apparatus is constructed.

The polarity of the coil 106 may be reversed with respect to that of the coil 10% by means of the reversing switch 110.

As illustrated current is supplied to the coils 106 and 104: in series from the power lines and The terminals of the secondary may be connected to the load for which the transformer is to be employed.

lln the operation of this form of the invention, when the coils 10 and 106 are arranged in series relation, with the same number of turns in each and with the polarity of the coils the same so that there is a buclning or opposing of the fluxes in the common limb 100 there is a neutralizing efiect as respects the magnetic lines of force in the bridge limb 100 so that the flux assumes a path traversing the entire outer limbs of the transformer thus passing through both exciting coils but without inducing any current flow in the secondary even though the secondary should be 'short-circuited. Under these conditions there is no output from the secondary but instead a counter-electromotive force is induced in the coils 10 i and 106 and the transformer is in the condition of the usual transformer at zero load. By changing the number of efiective turns in the coil 106 a certain proportion of the flux is caused to pass through the bridge limb 100 thus inducing a certain current flow in the secondary 11 2. V] hen the arm 108 is so adjusted that the main current supply does not pass through any of the turns of the coils 106 the transformer operates in the usual manner with the primary coils 104 and secondary coils 112 embracing the limbs 08 and 100 respectively of the transformer core.

The output of the transformer can be increased by reversing the polarity of the coil 106 by means of the reversing switch 110. The exciting influence of the coils 104 and 106 then becomes additive in the bridge limb 100 and the lines of force passing therethrough and in current inducing relation to the secondary coil 112 is the result of the combined actions of the coils 104 and 106 since the density of the lines of force in the bridge limb 100 under these conditions is the sum of the lines of force excited in the limb 98 by the coil 104 and in the limb 99 by the coil 106.

It will thus be seen that according to this form of the invention a current controlling mechanism of general application is provided, the mechanism permitting a variation in the possible output of the transformer from zero to the maximum output of the transformer.

In Fig. 2 we have illustrated a modification of our invention, wherein the limbs 14 and 13 of the main core receive the primary and secondary windings 18 and 20 respectively, the primary windings 18 embracing both limbs 13 and 14, the secondary windings embracing the limb 13. The auxiliary core comprises the limb 27 and yokes 28, with the yokes in magnetic conducting relation with the main magnetic core as in the other form of the invention. The auxiliary current correcting windings 30 are mounted upon the limb 27 as in the first form of the invention.

Various connections may be made for the purpose of including the various coils, the assembly shown in the present embodiment (Fig. 2) having certain definite advantages as stated below. This arrangement includes the conductors 89 and-90 leading respectively to the conductor 91 and main line 35. The conductor 91 leads to the main primary coils 18 which are in turn suitably connected to the other main power line 34 as will be understood. A short-circuiting switch 92 is provided for the purpose of shunting the current around the coils 30 when the switch is closed or, when the switch is open, causing the current to traverse the auxiliary coils 30 in series with the'main coils 18.

This device may be operated in various Ways to achieve different results. If it is desired to have an initial low secondary voltage the switch 92 may be closed thus short-circuiting the coil 30, in which case the current induced in the secondary 20 will be that resulting from the excitation of the main primary coils 18 only. If it is desired thereafter to increase the output of the transformer the-short-circuiting switch 92 may be opened thus increasing the magnetic lines of force in the common limb 13 to an extent-dependent upon the number of turns in the main coil 18 and auxiliary coil 30.

It will be understood that the reverse of this operation may take place and that the current induced in the secondary may be modified by suddenly closing the switch 92 thereby shunting the auxiliary coil 80.

The above operation has assumed the coils 80 and 18 being wound upon the limbs 14 and 27 respectively in the same directions so that they will produce corresponding flux movements at any particular instant in the common limb 13. This apparatus is particularly useful where the polarity of the winding 18 is reversed with respect to that of 30 so as to produce bucking or opposing lines of force in the common limb 13. This reversal may be accomplished b means of the usual reversin switch as in icated at 110, Fig. 1 applie across the conductors 89 and 90. Under these conditions, if an initial relatively high voltage is desired in the secondary 20 this may be accomplished by closing the switch 92 so that the main transformer operates in the usual manner with the primary coil 18 exciting magnetic lines of force in the main core, a current flow thereby being induced in the secondary coil 20. Opening of the switch 92 thereafter causes the primary current to pass through the auxiliary coil 30 thus producing bucking or opposing lines of force in the common limb 13, this action having the result of producing a new magnetic flux-path threading the outer limbs of the composite core. A relatively small flux flow will occur in the bridge limb 13 and a relatively small current flow will accordingly be induced in the secondary which is mounted upon the bridge or central limb 13 of the complete core since the volts per turn of the secondary are determined by the flux value in the portion of the core embraced by the secondary. Obviously the reverse of this operation may take place by having the switch 92 initially opened and thereafter closing the switch.

It will be noted that the extreme variations produced by the mechanism shown in Fig. 2 are produced without excessive arcing or excessive mechanical or electrical strains in the transformer since the primary circuit is at no time open but instead a complete closed primary circuit is provided at all times during which the apparatus is in use.

It is to be understood that either or both of the coils 18 and 30 may be provided with the usual five-point regulator or other device for varying the effective turns of either primary winding.

Any suitable housing (not shown) may be provided for the transformer.

From the above description it will be seen that we have provided for effectively decreasing or increasing the voltage and the current flow in the secondary coils of a transformer and that these variations will correspondingly limit the input or current flow in the primary coils. The mechanism permits the variation from zero to the possible maximum output of the transformer without creating severe electrical or mechanical strains in the apparatus. The current correcting or modifying apparatus which provides for varying the transformer conditions by directly influencing the fluxes performs its function without consuming any material amount of electrical energy.

This application is a division of our United States patent application Serial N 0. 174,778, filed March 12, 1927.

Having now described our invention, We claim:

In an alternating current electric transformer, a magnetizable core comprising outer limbs, a bridge limb and yokes connecting said limbs in the formation of two complete closed flux paths, primary coils on said outer limbs, means for connecting said primary coils in series relations, a secondary coil on said bridge limb, and means for changing the polarity of one of said primary coils with respect to the other.

Signed at Schenectady, in the county of Schenectady and State of New York, this 23rd day of January, A. D. 1928.

GEORGE A. THORNTON.

Signed at Lynn, in the county of Essex, and State of Massachusetts, this eighteenth day of January, A. D. nineteen hundred twenty-eight.

WOLOOTT REMINGTON. 

